It's more than 20 years since Prince Charles was ridiculed for saying that plants respond when spoken to.

Now the Royal Horticultural Society is putting his theory to the test. For the next month a group of tomato plants will be treated to a variety of MPs recordings through headphones attached to their pots. Their progress will be compared against another group of plants growing in silence.

The sounds will include poems, songs and nursery rhymes, as well as extracts from Shakespeare and The Day of the Triffids - John Wyndham's apocalyptic thriller in which plants take over the world.